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locking/rwsem: Add DEBUG_RWSEMS to look for lock/unlock mismatches

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For a rwsem, locking can either be exclusive or shared. The corresponding
exclusive or shared unlock must be used. Otherwise, the protected data
structures may get corrupted or the lock may be in an inconsistent state.

In order to detect such anomaly, a new configuration option DEBUG_RWSEMS
is added which can be enabled to look for such mismatches and print
warnings that that happens.

Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1522445280-7767-2-git-send-email-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Waiman Long
2018-03-30 17:27:58 -04:00
committed by Ingo Molnar
parent 169310f71f
commit 5149cbac42
3 changed files with 19 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
kernel/locking/rwsem.c
View File

@@ -117,6 +117,7 @@ EXPORT_SYMBOL(down_write_trylock);
void up_read(struct rw_semaphore *sem)
{
rwsem_release(&sem->dep_map, 1, _RET_IP_);
DEBUG_RWSEMS_WARN_ON(sem->owner != RWSEM_READER_OWNED);
__up_read(sem);
}
@@ -129,6 +130,7 @@ EXPORT_SYMBOL(up_read);
void up_write(struct rw_semaphore *sem)
{
rwsem_release(&sem->dep_map, 1, _RET_IP_);
DEBUG_RWSEMS_WARN_ON(sem->owner != current);
rwsem_clear_owner(sem);
__up_write(sem);
@@ -142,6 +144,7 @@ EXPORT_SYMBOL(up_write);
void downgrade_write(struct rw_semaphore *sem)
{
lock_downgrade(&sem->dep_map, _RET_IP_);
DEBUG_RWSEMS_WARN_ON(sem->owner != current);
rwsem_set_reader_owned(sem);
__downgrade_write(sem);
@@ -211,6 +214,7 @@ EXPORT_SYMBOL(down_write_killable_nested);
void up_read_non_owner(struct rw_semaphore *sem)
{
DEBUG_RWSEMS_WARN_ON(sem->owner != RWSEM_READER_OWNED);
__up_read(sem);
}

8
kernel/locking/rwsem.h
View File

@@ -16,6 +16,12 @@
*/
#define RWSEM_READER_OWNED ((struct task_struct *)1UL)
#ifdef CONFIG_DEBUG_RWSEMS
# define DEBUG_RWSEMS_WARN_ON(c) DEBUG_LOCKS_WARN_ON(c)
#else
# define DEBUG_RWSEMS_WARN_ON(c)
#endif
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
/*
* All writes to owner are protected by WRITE_ONCE() to make sure that
@@ -41,7 +47,7 @@ static inline void rwsem_set_reader_owned(struct rw_semaphore *sem)
* do a write to the rwsem cacheline when it is really necessary
* to minimize cacheline contention.
*/
if (sem->owner != RWSEM_READER_OWNED)
if (READ_ONCE(sem->owner) != RWSEM_READER_OWNED)
WRITE_ONCE(sem->owner, RWSEM_READER_OWNED);
}